@article{AL_1970_9_2_a4,
     author = {Z. K. Litvintseva},
     title = {The complexity of individual identity problems in semigroups},
     journal = {Algebra i logika},
     pages = {172--199},
     publisher = {mathdoc},
     volume = {9},
     number = {2},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1970_9_2_a4/}
}